Sum of sum | C # program to implement the above approach ; Function to find the sum ; Driver code
using System ; class GFG { static long sumOfSumSeries ( int n ) { return ( n * ( n + 1 ) * ( n + 2 ) ) / 6 ; } public static void Main ( String [ ] args ) { int N = 5 ; Console . Write ( sumOfSumSeries ( N ) ) ; } }